A critical review of three methods used for the measurement of mercury (Hg2+)-dissolved organic matter stability constants
J. D. Gasper, George R. Aiken, Joseph N. Ryan
2007, Applied Geochemistry (22) 1583-1597
Three experimental techniques - ion exchange, liquid-liquid extraction with competitive ligand exchange, and solid-phase extraction with competitive ligand exchange (CLE-SPE) - were evaluated as methods for determining conditional stability constants (K) for the binding of mercury (Hg2+) to dissolved organic matter (DOM). To determine the utility of a given method...
Estimated variability of National Atmospheric Deposition Program/Mercury Deposition Network measurements using collocated samplers
G.A. Wetherbee, D.A. Gay, R.C. Brunette, C.W. Sweet
2007, Environmental Monitoring and Assessment (131) 49-69
The National Atmospheric Deposition Program/Mercury Deposition Network (MDN) provides long-term, quality-assured records of mercury in wet deposition in the USA and Canada. Interpretation of spatial and temporal trends in the MDN data requires quantification of the variability of the MDN measurements. Variability is quantified for MDN data from collocated samplers...
Metal accumulation in the earthworm Lumbricus rubellus. Model predictions compared to field data
K. Veltman, M.A.J. Huijbregts, M.G. Vijver, W.J.G.M. Peijnenburg, P.H.F. Hobbelen, J.E. Koolhaas, C.A.M. van Gestel, P.C.J. van Vliet, Hendriks A. Jan
2007, Environmental Pollution (146) 428-436
The mechanistic bioaccumulation model OMEGA (Optimal Modeling for Ecotoxicological Applications) is used to estimate accumulation of zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) in the earthworm Lumbricus rubellus. Our validation to field accumulation data shows that the model accurately predicts internal cadmium concentrations. In addition, our results show...
Adaptive data-driven models for estimating carbon fluxes in the Northern Great Plains
B.K. Wylie, E. A. Fosnight, T.G. Gilmanov, A.B. Frank, J.A. Morgan, Marshall R. Haferkamp, T.P. Meyers
2007, Remote Sensing of Environment (106) 399-413
Rangeland carbon fluxes are highly variable in both space and time. Given the expansive areas of rangelands, how rangelands respond to climatic variation, management, and soil potential is important to understanding carbon dynamics. Rangeland carbon fluxes associated with Net Ecosystem Exchange (NEE) were measured from multiple year data sets at...
Three-dimensional P wave velocity model for the San Francisco Bay region, California
C.H. Thurber, T.M. Brocher, H. Zhang, V.E. Langenheim
2007, Journal of Geophysical Research B: Solid Earth (112)
[1] A new three-dimensional P wave velocity model for the greater San Francisco Bay region has been derived using the double-difference seismic tomography method, using data from about 5,500 chemical explosions or air gun blasts and approximately 6,000 earthquakes. The model region covers 140 km NE-SW by 240...
Global rates of habitat loss and implications for amphibian conservation
Alisa L. Gallant, R. W. Klaver, G.S. Casper, M.J. Lannoo
2007, Copeia (2007) 967-979
A large number of factors are known to affect amphibian population viability, but most authors agree that the principal causes of amphibian declines are habitat loss, alteration, and fragmentation. We provide a global assessment of land use dynamics in the context of amphibian distributions. We accomplished this by compiling global...
Competitive release and facilitation of drug-resistant parasites after therapeutic chemotherapy in a rodent malaria model
A. R. Wargo, S. Huijben, J. C. De Roode, J. Shepherd, A.F. Read
2007, Proceedings of the National Academy of Sciences of the United States of America (104) 19914-19919
Malaria infections frequently consist of mixtures of drug-resistant and drug-sensitive parasites. If crowding occurs, where clonal population densities are suppressed by the presence of coinfecting clones, removal of susceptible clones by drug treatment could allow resistant clones to expand into the newly vacated niche space within a host. Theoretical models...
A model for estimating passive integrated transponder (PIT) tag antenna efficiencies for interval-specific emigration rates
G.E. Horton, T.L. Dubreuil, B. H. Letcher
2007, Transactions of the American Fisheries Society (136) 1165-1176
Our goal was to understand movement and its interaction with survival for populations of stream salmonids at long-term study sites in the northeastern United States by employing passive integrated transponder (PIT) tags and associated technology. Although our PIT tag antenna arrays spanned the stream channel (at most flows) and were...
Spatiotemporal variability of stream habitat and movement of three species of fish
J.H. Roberts, P. L. Angermeier
2007, Oecologia (151) 417-430
Relationships between environmental variability and movement are poorly understood, due to both their complexity and the limited ecological scope of most movement studies. We studied movements of fantail (Etheostoma flabellare), riverweed (E. podostemone), and Roanoke darters (Percina roanoka) through two stream systems during two summers. We then related movement to...
Sediment delivery after a wildfire
Steven L. Reneau, D. Katzman, G.A. Kuyumjian, A. Lavine, D.V. Malmon
2007, Geology (35) 151-154
We use a record of sedimentation in a small reservoir within the Cerro Grande burn area, New Mexico, to document postfire delivery of ash, other fine-grained sediment carried in suspension within floods, and coarse-grained sediment transported as bedload over a five-year period. Ash...
Can modeling improve estimation of desert tortoise population densities?
K.E. Nussear, C.R. Tracy
2007, Ecological Applications (17) 579-586
The federally listed desert tortoise (Gopherus agassizii) is currently monitored using distance sampling to estimate population densities. Distance sampling, as with many other techniques for estimating population density, assumes that it is possible to quantify the proportion of animals available to be counted in any census. Because desert tortoises spend...
Seasonal nutrient and plankton dynamics in a physical-biological model of Crater Lake
K. Fennel, R. Collier, G. Larson, G. Crawford, E. Boss
2007, Hydrobiologia (574) 265-280
A coupled 1D physical-biological model of Crater Lake is presented. The model simulates the seasonal evolution of two functional phytoplankton groups, total chlorophyll, and zooplankton in good quantitative agreement with observations from a 10-year monitoring study. During the stratified period in summer and early fall the model displays a marked...
Remote camera-trap methods and analyses reveal impacts of rangeland management on Namibian carnivore communities
M. J. Kauffman, M. Sanjayan, J. Lowenstein, A. Nelson, R.M. Jeo, K.R. Crooks
2007, Oryx (41) 70-78
Assessing the abundance and distribution of mammalian carnivores is vital for understanding their ecology and providing for their long-term conservation. Because of the difficulty of trapping and handling carnivores many studies have relied on abundance indices that may not accurately reflect real abundance and distribution patterns. We developed statistical analyses...
Suspended sediment transport in an ephemeral stream following wildfire
D.V. Malmon, Steven L. Reneau, D. Katzman, A. Lavine, J. Lyman
2007, Journal of Geophysical Research F: Earth Surface (112)
We examine the impacts of a stand-clearing wildfire on the characteristics and magnitude of suspended sediment transport in ephemeral streams draining the burn area. We report the results of a monitoring program that includes 2 years of data prior to the Cerro Grande fire in...
Rapid plant diversity assessment using a pixel nested plot design: A case study in Beaver Meadows, Rocky Mountain National Park, Colorado, USA
M. A. Kalkhan, E.J. Stafford, T.J. Stohlgren
2007, Diversity and Distributions (13) 379-388
Geospatial statistical modelling and thematic maps have recently emerged as effective tools for the management of natural areas at the landscape scale. Traditional methods for the collection of field data pertaining to questions of landscape were developed without consideration for the parameters of these applications. We introduce an alternative field...
Pumping-induced drawdown and stream depletion in a leaky aquifer system
J.J. Butler Jr., X. Zhan, V.A. Zlotnik
2007, Ground Water (45) 178-186
The impact of ground water pumping on nearby streams is often estimated using analytic models of the interconnected stream-aquifer system. A common assumption of these models is that the pumped aquifer is underlain by an impermeable formation. A new semianalytic solution for drawdown and stream depletion has been developed that...
Characterization of methane hydrate host sediments using synchrotron-computed microtomography (CMT)
K.W. Jones, H. Feng, S. Tomov, W.J. Winters, M. Prodanovic, D. Mahajan
2007, Journal of Petroleum Science and Engineering (56) 136-145
The hydrate-sediment interaction is an important aspect of gas hydrate studies that needs further examination. We describe here the applicability of the computed microtomography (CMT) technique that utilizes an intense X-ray synchrotron source to characterize sediment samples, two at various depths from the Blake Ridge area (a well-known hydrate-prone region)...
On the formation and structure of rare-earth element complexes in aqueous solutions under hydrothermal conditions with new data on gadolinium aqua and chloro complexes
Robert A. Mayanovic, Alan J. Anderson, William A. Bassett, I.-M. Chou
2007, Chemical Geology (239) 266-283
Synchrotron X-ray spectroscopy experiments were made on the Gd(III) aqua and chloro complexes in low pH aqueous solutions at temperatures ranging from 25 to 500????C and at pressures up to 480??MPa using a hydrothermal diamond anvil cell. Analysis of fluorescence Gd L3-edge X-ray absorption fine structure (XAFS) spectra measured from...
Improved wetland remote sensing in Yellowstone National Park using classification trees to combine TM imagery and ancillary environmental data
C. Wright, Alisa L. Gallant
2007, Remote Sensing of Environment (107) 582-605
The U.S. Fish and Wildlife Service uses the term palustrine wetland to describe vegetated wetlands traditionally identified as marsh, bog, fen, swamp, or wet meadow. Landsat TM imagery was combined with image texture and ancillary environmental data to model probabilities of palustrine wetland occurrence in Yellowstone National Park using classification...
Wellsite, laboratory, and mathematical techniques for determining sorbed gas content of coals and gas shales utilizing well cuttings
K.D. Newell
2007, Natural Resources Research (16) 55-66
Drill cuttings can be used for desorption analyses but with more uncertainty than desorption analyses done with cores. Drill cuttings are not recommended to take the place of core, but in some circumstances, desorption work with cuttings can provide a timely and economic supplement to that of cores. The mixed...
Effects of management and climate on elk brucellosis in the Greater Yellowstone Ecosystem
P.C. Cross, W.H. Edwards, B.M. Scurlock, E.J. Maichak, J.D. Rogerson
2007, Ecological Applications (17) 957-964
Every winter, government agencies feed ∼6000 metric tons (6 × 106 kg) of hay to elk in the southern Greater Yellowstone Ecosystem (GYE) to limit transmission of Brucella abortus, the causative agent of brucellosis, from elk to cattle. Supplemental feeding, however, is likely to increase the transmission of brucellosis in...
Using simulated historical time series to prioritize fuel treatments on landscapes across the United States: The LANDFIRE prototype project
Robert E. Keane, Matthew Rollins, Zhi-Liang Zhu
2007, Ecological Modelling (204) 485-502
Canopy and surface fuels in many fire-prone forests of the United States have increased over the last 70 years as a result of modern fire exclusion policies, grazing, and other land management activities. The Healthy Forest Restoration Act and National Fire Plan establish a national commitment to reduce fire hazard...
Using biodynamic models to reconcile differences between laboratory toxicity tests and field biomonitoring with aquatic insects
D.B. Buchwalter, Daniel J. Cain, W.H. Clements, S. N. Luoma
2007, Environmental Science & Technology (41) 4821-4828
Aquatic insects often dominate lotic ecosystems, yet these organisms are under-represented in trace metal toxicity databases. Furthermore, toxicity data for aquatic insects do not appear to reflect their actual sensitivities to metals in nature, because the concentrations required to elicit toxicity...
Intertidal sand body migration along a megatidal coast, Kachemak Bay, Alaska
P.N. Adams, P. Ruggiero, G.C. Schoch, G. Gelfenbaum
2007, Journal of Geophysical Research F: Earth Surface (112)
[1] Using a digital video-based Argus Beach Monitoring System (ABMS) on the north shore of Kachemak Bay in south central Alaska, we document the timing and magnitude of alongshore migration of intertidal sand bed forms over a cobble substrate during a 22-month observation period. Two...
Reconstructing late Cenozoic stream gradients from high-level chert gravels in central Eastern Kansas
J.W. Harbaugh, D. F. Merriam, H.H. Howard
2007, Current Research in Earth Sciences (253)
Interpreting the evolution of Kansas' landscape east of the Flint Hills provides major challenges. In the Neogene (late Tertiary) and perhaps part of the Pleistocene, streams transported a variety of sedimentary materials, including chert gravels derived from the Flint Hills. Gentle intermittent uplift stimulated the system system to cut down,...
